The present invention relates to material handling and, in particular, to methods and apparatuses for conveying packages and a mechanism for controlling the location of packages on a conveyor.
It is conventional to convey large numbers of packages at high speed, especially in the parcel delivery industry, wherein the packages are sorted according to desired categories. The efficiency with which the packages are handled can be seriously diminished when jam-ups of packages occur that require that conveyor lines be shut down until the jam has been cleared.
While a jam-free conveyance of packages along the straight flights of a conveyor is relatively easily accomplished, problems can occur at turns where wide packages present a serious risk of jamming. The sharper the turn the greater the risk.
Measures to minimize this risk have been taken, such as that disclosed in Ydoate et al. U.S. Pat. No. 5,222,586, the disclosure of which is incorporated herein by reference. As depicted in FIGS. 1-4, a conveyor junction 10 for packages comprises an upstream conveyor 12, a downstream conveyor 14, and an intermediate conveyor 16, each having a conveying surface. The conveyors 12, 14, 16 preferably comprise suitably driven conveyor mechanisms, such as a solid or mesh belt or a series of driven rollers. The upstream conveyor 12 extends around a drive drum 22, and the downstream conveyor 14 extends around a drive drum 24.
Extending along one side of the conveyors 12, 14, 16 is an upright side wall 26. The upstream conveyor 12 receives packages P from a conveyor (not shown) which is intended to align the packages in the direction of travel and position the packages in single file along the side wall 26. The side wall thus guides the packages and defines a reference line along which inner edges of the packages travel.
Occasionally, however, it occurs that instead of being positioned in single file, some of the packages may be conveyed abreast of one another, i.e., in side-by-side relationship. For example, the packages P1, P2 are traveling abreast. The combined width CW occupied by those two packages may present a problem at a downstream location in the conveyor system, especially around turns by creating a jam.
Also, a single package P3 depicted in FIG. 3 may be of such a large width W' that it might jam in the downstream turns.
The risk that the abreast packages P1, P2, or the excessively wide package P3 may jam downstream is prevented by the conveyor junction 10, wherein the width W1 of the upstream conveyor is larger than each of the widths W2 and W3 of the downstream and intermediate conveyors 14, 16, and wherein the width W3 of the intermediate conveyor is less than one-half of the width W2 of the downstream conveyor 14. Those widths are measured from the reference line defined by the guide wall 26 to an outer edge of the respective conveyors 12, 14, 16.
As a result, in the case of packages P1, P2 traveling abreast, the outer package P2 (i.e., the package farthest from the side wall 26) will have its center of gravity situated outside of the outer edge 28 of the intermediate conveyor 16 and will fall off that conveyor into a drop-off zone 30 as depicted in FIG. 2. A ramp 32 is situated in the drop-off zone to guide the package P2 when it falls off the intermediate conveyor 16. The discharged package P2 can then be manually replaced onto the conveyor system. Alternatively, the packages can fall onto another conveyor which transports the packages to a suitable location.
The length L of the intermediate conveyor should be made larger than the length of the longest package anticipated to be conveyed.
The exceptionally wide package P3, depicted in FIG. 3, has a width W' greater than the width W2 of the downstream conveyor, whereby its center of gravity CG is situated outside of the edge 28 of the intermediate conveyor (assuming a substantially uniform distribution of the weight of the package contents as is generally the case). That package will, therefore, fall down the chute, as depicted in FIG. 3.
This tends to ensure that the packages reaching the downstream conveyor 14 will be in single file and will present a width which is less than the width W2 of the downstream conveyor. Consequently, the risk of jams occurring downstream of the intermediate conveyor, especially during turns, will be minimized.
In order to expedite the egress of packages from the intermediate conveyor 16, a discharge accelerator may be provided, as depicted in FIG. 4. The discharge accelerator comprises a roller 40 which is driven in a direction tending to frictionally displace a falling package downwardly. The roller 40 is rotated about an axis extending parallel to the reference line defined by the wall 26 by means of a motor 42. In order to ensure that the packages do not engage the roller 40 unless they are actually falling from the intermediate conveyor, the roller 40 is disposed at a lower elevation than the convening surface of the intermediate conveyor.
Although the afore-described apparatus has performed with beneficial results, room for improvement remains. That is, in order for a package to be discharged into the drop-off zone 30, its center of gravity must be situated outside of the outer edge 28, so that the package tilts downwardly. In dealing with that requirement, the above-described apparatus assumes that the center of gravity of each package is disposed at its geometric center. In reality, however, that is not always the case, and it would be desirable to provide a system which deals with situations in which the center of gravity is offset from the geometrical center.
Also, since the afore-mentioned apparatus requires that a package tilt and fall downwardly in order to be rejected, a certain minimum vertical height of the apparatus is required which might not be desirable in some situations involving restricted height conditions. Therefore, an apparatus which requires less height would be advantageous in some applications.